i am stuck on how to weight paint my human character using the rigify add-on
The metarig is only used to lay out the bones on the mesh. I recommend a tutorial if you're not familiar with Rigify.
Place the character model so that it stands on the &quot;ground&quot; (soles of the feet at z=0). Make sure you have applied All Transformations (scale, location, rotation) to the mesh with Ctrl+A (in Object mode) before you start. The bones of the elbows and knees should be bent slightly.
When you're happy with the layout, apply All Transformations to the metarig, then press the Generate Rig button. You can use this button more than once. Rigify can override the generated rig. See section button Advanced Options.
The Generate Rig button creates the actual rig. It's just named &quot;rig&quot; and has all the control bones and deform bones (layer 30) on different layers.
After you have created the generated rig you can parent it to the mesh with Automatic Weights and test it in Pose mode.
There might be some issues that need to be fixed.

The fingers might need some corrections. To make the fingers &quot;grab&quot; you need to scale the red handle. If it doesn't work proper have a look here: Rigify finger controls rotation not moving correctly

The eye lids you might have to weight paint manually. And you need to parent the eyeballs to a bone of the rig to make them follow the control. Video: Fixing the Metarig - The SECRETS of RIGIFY: Part 3 and Weight Painting - The SECRETS of RIGIFY: Part 4! - [Blender 2.8]

The teeth and tongue might need some weight painting